At present, soft switching architecture is applied widely. The soft switching architecture separates carrying function from controlling function. The carrying function is implemented by a media gateway, MG. That is, the MG mainly provides an access adaptation function, a media stream conversion function interacting with other networks, and provides specific media resources. While the controlling function is realized by a media gateway controller, MGC. That is, the MGC may control, with signaling, a MG to carry out various service operations, so as to realize control over a calling process.
An MG is provided with resources required for implementing calls. In the soft switching architecture, resources are abstracted as terminations. Therefore, according to usage of resources, a termination in a MG may be a resource with semi-permanent existence such as time division multiplex (TDM) channels, or a resource that is temporarily applied and released after use, such as real-time transport protocol (RTP) streams. In the soft switching architecture, combination of various terminations is abstracted as a context, that is, the context includes topological relationship among terminations. Thus, for a call, each call connection operation carried out by a MG is practically to connect relevant terminations in the context corresponding to the call. For example, referring to FIG. 1, when a call connection is set up for a calling party a and a called party b, on the MG, resources used by the calling party a, i.e. terminations, include a TDM channel a and a RTP stream a, and resources used by the called party b, i.e. terminations, include a TDM channel b and a RTP stream b. Therefore, when the MG sets up the call connection, it must connect the termination TDM channel a with the termination RTP stream a in the context a corresponding to the calling party a, and connect the termination TDM channel b with the termination RTP stream b in the context b corresponding to the called party b.
As can be seen, the process that a MG sets up termination connection in a context corresponding to a call is an important process in a call connection processes. At present, a MG carries out the termination connection process under the control of a MGC.
FIG. 2 is a flow chart showing a conventional process of instructing a MG to set up termination connections. Referring to FIG. 2, the conventional process of a MGC instructing a MG to set up termination connections includes the following steps.
Step 201: When a call connection is required, the MGC transmits to the MG information on the terminations that need to be connected, by carrying it in a connection indication.
Here, referring to FIG. 3, for example, the MGC carries the termination TDM channel a used by the calling party a and the termination TDM channel b used by the called party b as the information on the terminations that need to be connected into the connection indication, and transmits it to the MG.
Step 202: After the MG receives the connection indication carrying the information on the terminations that need to be connected, the MG determines whether the MG itself has capabilities for connecting the terminations indicated in the connection indication. If so, Step 203 is carried out; otherwise, Step 204 is carried out.
Here, for various types of terminations, the MG has connection capabilities for some types of these terminations, and does not have connection capabilities for others types of these terminations. For example, referring to FIG. 3, the MG has a connection capability for connecting a termination representing TDM channel with a termination representing RTP stream, while does not have a capability for connecting terminations representing two TDM channels due to lacking of related inter-switching logics. At this time, even if the MG receives the connection indication for connecting the termination TDM channel a with the TDM channel b sent from the MGC, this connection operation cannot be implemented.
Step 203: The MG connects the terminations in a context corresponding to the current call, and the current procedure ends up.
Step 204: The MG transmits a failure response to the MGC.
As can be seen from the above, although the MG has a large number of terminations representing various resources, the MG itself may not have the capability to connect any two terminations. However, when a MGC instructs a MG to connect two specific terminations in a conventional manner, whether the MG has the capability to connect the two specific terminations is not taken into account. Therefore, the MG tends to fail to implement the connection operation due to lacking the capability for connecting the two specific terminations, thereby resulting in failure of a call connection and greatly decreasing quality of service.